linux-kernel - Re: [PATCH 12/14] phy: qcom-qmp-combo: rename common-register pointers

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Message-ID: <Y3JkDt9xMVMhUJPs@hovoldconsulting.com>
Date:   Mon, 14 Nov 2022 16:51:42 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/14] phy: qcom-qmp-combo: rename common-register
 pointers

On Mon, Nov 14, 2022 at 06:38:36PM +0300, Dmitry Baryshkov wrote:
> On 14/11/2022 15:54, Johan Hovold wrote:
> > On Sat, Nov 12, 2022 at 02:31:27PM +0300, Dmitry Baryshkov wrote:
> >> On 11/11/2022 12:24, Johan Hovold wrote:
> >>> The common registers are shared by the USB and DP parts of the PHY so
> >>> drop the misleading "dp" prefix from the corresponding pointers.
> >>>
> >>> Note that the "DP" prefix could also be dropped from the corresponding
> >>> defines, but leave that in place for now.
> >>>
> >>> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> >>> ---
> >>>    drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 24 +++++++++++------------
> >>>    1 file changed, 12 insertions(+), 12 deletions(-)
> >>
> >> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >>
> >> Note regarding the last phrase: I'd suggest leaving the DP prefix in
> >> register names, it makes it easier to visually note & verify the
> >> register block.
> > 
> > My point is that "DP" was never part of the COM register block name. The
> > confusion likely comes from the vendor driver naming these defines along
> > the lines of
> > 
> > 	USB3_DP_COM_POWER_DOWN_CTRL
> > 
> > Here "USB3_DP" is the common prefix for all defines that apply to both
> > "parts" of the PHY so the corresponding Linux define
> > 
> > 	QPHY_V3_DP_COM_POWER_DOWN_CTRL
> > 
> > should either include "USB3" or drop "DP".
> 
> My thought was that we already have too many _COM_ defines in the qmp 
> headers. Having QPHY_Vn_COM_something would make it too easy to mix it 
> with QSERDES_Vn_COM_foo. Thus I'd vote to leave DP_COM prefix in place. 
> While it might be not fully accurate, it serves the point of identifying 
> the register block.

I don't mind terribly and I didn't even consider trying to rename the
current defines.

The lack of public conclusive documentation makes structuring this mess
much harder than it should have to be. 

That said, I don't really think that the risk of mixing up
QPHY_Vn_COM_foo with QSERDES_Vn_COM_bar is something we need to worry
about as you already have a separating "QSERDES" in there. Those sets of
registers should be disjoint too if I remember correctly.

> > This becomes more apparent on SC8280XP where the corresponding define
> > is:
> > 
> > 	USB43DP_COM_POWER_DOWN_CTRL
> 
> I'd still use something like QPHY_V10_DP_COM_POWER_DOWN_CTRL here.

Yeah, but then you're just making names up. ;)

Johan